Bibliografie tematiche / Stars of low metallicity

Letteratura scientifica selezionata sul tema "Stars of low metallicity"

Autore: Grafiati

Pubblicato: 8 giugno 2024

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili

Scegli il tipo di fonte:

Consulta la lista di attuali articoli, libri, tesi, atti di convegni e altre fonti scientifiche attinenti al tema "Stars of low metallicity".

Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.

Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.

Articoli di riviste sul tema "Stars of low metallicity":

Pakmor, Rüdiger, Christine M. Simpson, Freeke van de Voort, Lars Hernquist, Lieke van Son, Martyna Chruślińska, Rebekka Bieri, Selma E. de Mink e Volker Springel. "Formation and fate of low-metallicity stars in TNG50". Monthly Notices of the Royal Astronomical Society 512, n. 3 (16 marzo 2022): 3602–15. http://dx.doi.org/10.1093/mnras/stac717.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

ABSTRACT Low-metallicity stars give rise to unique spectacular transients and are of immense interest for understanding stellar evolution. Their importance has only grown further with the recent detections of mergers of stellar mass black holes that likely originate mainly from low-metallicity progenitor systems. Moreover, the formation of low-metallicity stars is intricately linked to galaxy evolution, in particular to early enrichment and to later accretion and mixing of lower metallicity gas. Because low-metallicity stars are difficult to observe directly, cosmological simulations are crucial for understanding their formation. Here, we quantify the rates and locations of low-metallicity star formation using the high-resolution TNG50 magnetohydrodynamical cosmological simulation, and we examine where low-metallicity stars end up at z = 0. We find that $20{{\ \rm per\ cent}}$ of stars with $Z_*\lt 0.1\, \mathrm{Z_\odot }$ form after z = 2, and that such stars are still forming in galaxies of all masses at z = 0 today. Moreover, most low-metallicity stars at z = 0 reside in massive galaxies. We analyse the radial distribution of low-metallicity star formation and discuss the curious case of seven galaxies in TNG50 that form stars from primordial gas even at z = 0.

Sabach, Efrat. "Jsolated Stars of Low Metallicity". Galaxies 6, n. 3 (15 agosto 2018): 89. http://dx.doi.org/10.3390/galaxies6030089.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

We study the effects of a reduced mass-loss rate on the evolution of low metallicity Jsolated stars, following our earlier classification for angular momentum (J) isolated stars. By using the stellar evolution code MESA we study the evolution with different mass-loss rate efficiencies for stars with low metallicities of Z = 0 . 001 and Z = 0 . 004 , and compare with the evolution with solar metallicity, Z = 0 . 02 . We further study the possibility for late asymptomatic giant branch (AGB)—planet interaction and its possible effects on the properties of the planetary nebula (PN). We find for all metallicities that only with a reduced mass-loss rate an interaction with a low mass companion might take place during the AGB phase of the star. The interaction will most likely shape an elliptical PN. The maximum post-AGB luminosities obtained, both for solar metallicity and low metallicities, reach high values corresponding to the enigmatic finding of the PN luminosity function.

Bouret, J. C., T. Lanz, F. Martins, W. L. F. Marcolino, D. J. Hillier, E. Depagne e I. Hubeny. "Massive stars at low metallicity". Astronomy & Astrophysics 555 (18 giugno 2013): A1. http://dx.doi.org/10.1051/0004-6361/201220798.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Hirschi, R. "Very low-metallicity massive stars:". Astronomy & Astrophysics 461, n. 2 (9 ottobre 2006): 571–83. http://dx.doi.org/10.1051/0004-6361:20065356.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Hirschi, Raphael, Cristina Chiappini, Georges Meynet, André Maeder e Sylvia Ekström. "Stellar Evolution at Low Metallicity". Proceedings of the International Astronomical Union 3, S250 (dicembre 2007): 217–30. http://dx.doi.org/10.1017/s1743921308020528.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

AbstractMassive stars played a key role in the early evolution of the Universe. They formed with the first halos and started the re-ionisation. It is therefore very important to understand their evolution. In this review, we first recall the effect of metallicity (Z) on the evolution of massive stars. We then describe the strong impact of rotation induced mixing and mass loss at very low Z. The strong mixing leads to a significant production of primary 14N, 13C and 22Ne. Mass loss during the red supergiant stage allows the production of Wolf-Rayet stars, type Ib,c supernovae and possibly gamma-ray bursts (GRBs) down to almost Z = 0 for stars more massive than 60 M⊙. Galactic chemical evolution models calculated with models of rotating stars better reproduce the early evolution of N/O, C/O and 12C/13C. Finally, the impact of magnetic fields is discussed in the context of GRBs.

Garcia, Miriam, Artemio Herrero, Francisco Najarro, Inés Camacho, Daniel J. Lennon, Miguel A. Urbaneja e Norberto Castro. "Low-metallicity (sub-SMC) massive stars". Proceedings of the International Astronomical Union 12, S329 (novembre 2016): 313–21. http://dx.doi.org/10.1017/s1743921317003088.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

AbstractThe double distance and metallicity frontier marked by the SMC has been finally broken with the aid of powerful multi-object spectrographs installed at 8-10m class telescopes. VLT, GTC and Keck have enabled studies of massive stars in dwarf irregular galaxies of the Local Group with poorer metal-content than the SMC. The community is working to test the predictions of evolutionary models in the low-metallicity regime, set the new standard for the metal-poor high-redshift Universe, and test the extrapolation of the physics of massive stars to environments of decreasing metallicity. In this paper, we review current knowledge on this topic.

Karakas, Amanda I., Maria Lugaro e Simon W. Campbell. "The slow-neutron capture process in low-metallicity asymptotic giant branch stars". Proceedings of the International Astronomical Union 5, S265 (agosto 2009): 57–60. http://dx.doi.org/10.1017/s1743921310000165.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

AbstractElements heavier than iron are produced in asymptotic giant branch (AGB) stars via the slow neutron capture process (s process). Recent observations of s-process-enriched Carbon Enhanced Metal-Poor (CEMP) stars have provided an unprecedented wealth of observational constraints on the operation of the s-process in low-metallicity AGB stars. We present new preliminary full network calculations of low-metallicity AGB stars, including a comparison to the composition of a few s-process rich CEMP stars. We also discuss the possibility of using halo planetary nebulae as further probes of low-metallicity AGB nucleosynthesis.

Bomans, Dominik J., e Kerstin Weis. "Massive variable stars at very low metallicity?" Proceedings of the International Astronomical Union 6, S272 (luglio 2010): 265–70. http://dx.doi.org/10.1017/s1743921311010519.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

AbstractObservational contraints on the evolution and instabilities of massive stars at very low metallicities are limited. Most of the information come from HST observations of one target, I Zw 18. Recent distance estimates of I Zw 18 put it at 17 Mpc, moving detailed studies of single stars clearly beyond the range of current ground based telescopes. Since massive stars with metallcities of 1/10 of solar and below are our best proxies for massive stars in (proto-) galaxies around the time of reionization, finding them and studying their evolution and instabilities is of premium importance for our understanding of galaxy formation, feedback, and the IGM reionization. Here we present pilot study results of variable stars in two more nearby extremely low metallicity galaxies, UGC 5340 and UGCA 292, and comment on the possibilities of more detailed studies of variable massive stars with new ground-based instrumentation.

Yang, Ming, Alceste Z. Bonanos, Biwei Jiang, Man I. Lam, Jian Gao, Panagiotis Gavras, Grigoris Maravelias et al. "Evolved massive stars at low-metallicity". Astronomy & Astrophysics 647 (marzo 2021): A167. http://dx.doi.org/10.1051/0004-6361/202039596.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

We present a case study in which we used a novel method to identify red supergiant (RSG) candidates in NGC 6822 based on their 1.6 μm H-bump. We collected 32 bands of photometric data for NGC 6822 ranging from the optical to the mid-infrared, derived from Gaia, PS1, LGGS, VHS, UKIRT, IRSF, HAWK-I, Spitzer, and WISE. Using the theoretical spectra from MARCS, we demonstrate that there is a prominent difference around 1.6 μm (H-bump) between targets with high and low surface gravity (HSG and LSG). Taking advantage of this feature, we identify efficient color–color diagrams of rzH (r − z vs. z − H) and rzK (r − z vs. z − K) to separate HSG (mostly foreground dwarfs) and LSG targets (mainly background red giant stars, asymptotic giant branch stars, and RSGs) from crossmatching of optical and near-infrared (NIR) data. Moreover, synthetic photometry from ATLAS9 gives similar results. We further separated RSG candidates from the remaining LSG candidates as determined by the H-bump method by using semi-empirical criteria on NIR color–magnitude diagrams, where both the theoretic cuts and morphology of the RSG population are considered. This separation produced 323 RSG candidates. The simulation of foreground stars with Besançon models also indicates that our selection criteria are largely free from the contamination of Galactic giants. In addition to the H-bump method, we used the traditional BVR method (B − V vs. V − R) as a comparison and/or supplement by applying a slightly aggressive cut to select as many RSG candidates as possible (358 targets). Furthermore, the Gaia astrometric solution was used to constrain the sample, where 181 and 193 targets were selected with the H-bump and BVR method, respectively. The percentages of selected targets in the two methods are similar at ∼60%, indicating a comparable accuracy of the two methods. In total, there are 234 RSG candidates after combining targets from the two methods, and 140 (∼60%) of them are in common. The final RSG candidates are in the expected locations on the mid-infrared color–magnitude diagram with [3.6]−[4.5] ≲ 0 and J − [8.0] ≈ 1.0. The spatial distribution is also coincident with the far-ultraviolet-selected star formation regions, suggesting that the selection is reasonable and reliable. We indicate that our method can also be used to identify other LSG targets, such as red giants and asymptotic giant branch stars, and it can also be applied to most of the nearby galaxies by using recent large-scale ground-based surveys. Future ground- and space-based facilities may promote its application beyond the Local Group.

Bonifacio, P. "Low Metallicity Stars in our Galaxy". EAS Publications Series 24 (2007): 251–61. http://dx.doi.org/10.1051/eas:2007034.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Più fonti

Tesi sul tema "Stars of low metallicity":

Masters, Craig Eugene Ashman Keith M. "The formation of low metallicity globular clusters". Diss., UMK access, 2007.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Thesis (Ph. D.)--Dept. of Physics and Dept. of Mathematics. University of Missouri--Kansas City, 2007.
"A dissertation in physics and mathematics." Advisor: Keith M. Ashman. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Nov. 13, 2007. Includes bibliographical references (leaves 67-70). Online version of the print edition.

Szécsi, Dorottya [Verfasser]. "The evolution of low-metallicity massive stars / Dorottya Szécsi". Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/1113688262/34.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Fukushima, Hajime. "Radiative feedback from massive stars in low-metallicity environments". Kyoto University, 2019. http://hdl.handle.net/2433/242603.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Krawchuk, Curtis A. P. "The determination of metallicity and temperature of low-mass stars using broad-band photometry". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0035/MQ27361.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Lindgren, Sara. "Metallicity determination of M dwarfs". Doctoral thesis, Uppsala universitet, Observationell astrofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-332102.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

M dwarfs constitute around 70% of all stars in the local Galaxy. Their multitude together with their long main-sequence lifetimes make them important for studies of global properties of the Galaxy such as the initial mass function or the structure and kinematics of stellar populations. In addition, the exoplanet community is showing an increasing interest for those small, cold stars. However, very few M dwarfs are well characterized, and in the case of exoplanetary systems the stellar parameters have a direct influence on the derived planet properties. Stellar parameters of M dwarfs are difficult to determine because of their low surface temperatures that result in an optical spectrum dominated by molecular lines. Most previous works have therefore relied on empirical calibrations. High-resolution spectrographs operating in the infrared, a wavelength region less affected by molecular lines, have recently opened up a new window for the investigation of M dwarfs. In the two first papers of this thesis we have shown that we can determine the metallicity, and in some cases the effective temperature, using synthetic spectral fitting with improved accuracy. This method is time consuming and therefore not practical or even feasible for studies of large samples of M dwarfs. When comparing our results from the high-resolution studies with available photometric calibrations we find systematic differences. In the third paper we therefore used our sample to determine a new photometric metallicity calibration. Compared to previous calibrations our new photometric calibration shows improved statistical characteristics, and our calibration gives similar results as spectroscopic calibrations. In a comparison with theoretical calculations we find a good agreement of the shapes and slopes of iso-metallicity lines with our empirical relation. Applying the photometric calibration to a sample of M dwarfs with confirmed exoplanets we find a possible giant planet-metallicity correlation for M dwarfs.

Verdugo, Salgado Celia Anahi. "Star formation in low gas density and low metallicity environments". Observatoire de Paris, 2015. https://hal.science/tel-02095302.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Dans les galaxies proches, la relation empirique de Kennicutt-Schmidt (KS) a été établie entre la densité surfacique de formation d’étoiles et la densité surfacique de gaz. Elle est forte et presque linéaire quand on considère le gaz moléculaire (H2) mais devient moins valable lorsque l’hydrogène n’est qu’atomique (HI). Ces régions de densité de gaz faible sont d’une importance cruciale dans le domaine de la formation d’étoiles, car elles possèdent les mêmes conditions que dans les galaxies de l’univers jeune, de faible métallicité. Cette thèse compile les données observationnelles obtenues au télescope de 30 m. De l’IRAM sur deux types de régions distinctes : les galaxies à disque ayant une émission ultra-violet étendue (XUV), et le milieu interstellaire déplacé dans le milieu intra-amas (ICM) chaud sous l’effet du balayage de la pression dynamique dans l’amas de la Vierge. Pour déterminer la présence des molécules H2 et afin d’étudier la relation KS dans ces régions, des observations de CO ont été faites dans les parties externes des galaxies XUV, et nous avons à la fois des détections et des limites supérieures. Les relations KS ont montré une loi de puissance discontinue pour des densités de gaz faibles, en dessous du seuil de la transition de phase HI-H2. Dans l’amas de la Vierge, des observations similaires de Co ont été faites le long des bras marée qui relient NGC4388 et M86, où aucune présence de H2 n’est attendue. Nous avons effectué des détections, montrant une efficacité de formation d’étoiles très faible, et montrant de nouveau une discontinuité de la relation KS pour des densités de gaz faibles, prouvant que les processus bien connus de consommation du gaz à forte densité ne peuvent être généralisés aux densités plus faibles. D’autre part, nos résultats montrent que le gaz H2 peut survivre un temps long que prévu dans l’ICM hostile
In nearby galaxies, an empirical relation has been established between star formation and gas surface densities, the Kennicutt-Schmidt (KS). The relation is nearly linear when molecular gas (H2) is considered, while is less tight with atomic hydrogen (HI). These low gas density regions are of a key importance in the field of star formation, since the are also low metallicity environments, resembling the conditions of a younger universe. This thesis summarizes the observational work done with the IRAM 30MT telescope in two kinds of such regions : disk galaxies with extended ultra-violet emission (XUV), and the interstellar medium going into the hot intra-cluster medium (ICM) under ram-pressure stripping in the Virgo cluster. The galex telescope has unveiled in far ultra-violet (FUV) star formation in the outer parts of some disk galaxies that was not traced by HA. To determine the presence of H2 and analyse the K-S relation in these regions, CO observations where done in the outskirts of several XUV disk galaxies, finding both detections and upper limits. These K-S relations showed a broken power law at low gas densities, below the HI-H2 threshold. In the Virgo cluster, similar CO observations were done along the HI tidal arm connecting NGC4388 and M86, where no H2 is expected. Two detections were found, showing very low star formation efficiencies (depleting less than 0,1 % of the gas reservoir per 10 [exposant] 8 yr), and showing again a disconuity of the K-S relation at low gas densities, probing that the process of a gas consumption into stars well known at high densities cannot be extrapolated to lower densities, and that H2 can survive a certain time in the hostile ICM

Rajpurohit, Arvind Singh. "Low-mass stars as tracers of the milky way populations : investigating the effects of metallicity in cool atmosphere". Thesis, Besançon, 2013. http://www.theses.fr/2013BESA2023/document.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Les étoiles de petite masse (naines M) forment la composante stellaire dominante de notre galaxie et contribuent à la majeure partie de la matière baryonique dans la galaxie. Notre compréhension de la galaxie repose donc sur la connaissance de cette composante peu lumineuse. Par ailleurs, un nombre grandissant d’exoplanètes sont découverte autour de naines M, y compris des super-terres. L’étude des naines M a ainsi des implications importantes sur la physique stellaire, permettant de comprendre les processus en jeu dans ces atmosphères froides. Ces astres restent cependant peu connus du fait de leur faible luminosité intrinsèque. La description de ces étoiles nécessite une validation empirique fort, notamment en ce qui concerne les effets de l’abondance chimique sur la physique des atmosphères froides.Le but de cette thèse est de déterminer les paramètres fondamentaux des naines M et de tester les modèles d’atmosphères d’étoiles froides.Dans la première partie nous comparons des spectres calibrés dans le visible et l’infrarouge des composantes de système triple LHS 1070 avec des spectres synthétiques. Cette étude permet d’améliorer notre compréhension de la formation de la poussière dans les atmosphères très froides. Ce travail est étendu à un échantillon de naines M et permet de déterminer l’échelle de température des naines M. La seconde partie présente l’analyse des spectres à haute résolution de 21 naines M de faible métallicité (sous naines). Nous analysons en détail les signature moléculaires et atomiques dans le spectre. La comparaison avec des spectres synthétiques permet de mesurer les paramètres stellaires des étoiles et de déterminer avec précision leur métallicité. Ce travail doit initier des recherches futures. En particulier nous voulons étendre cette étude dans le domaine proche-infrarouge pour s’assurer que les résultats obtenus sont cohérents du domaine optique jusqu’à l’infrarouge proche
Very Low-Mass stars (M dwarfs) are an important source of information for probing the lowmass end of the main sequence, down to the hydrogen burning limit. They are the dominantstellar component of the Galaxy and make up the majority of baryonic matter in the Galaxy.Moreover, an increasing number of M dwarfs are now known to host exoplanets, includingsuper-Earth exoplanets. The determination of accurate fundamental parameters for M dwarfshas therefore relevant implications for both stellar and Galactic astronomy as well as planetology.Despite their large number in the Galaxy, M dwarfs remain elusive objects and themodelling of their photosphere has long remained a challenge (molecular opacities, dust cloudformation). The description of these stars therefore need a strong empirical basis, or validation.In particular, the effect of metallicity on the physics of cool atmospheres are still poorly known,even for early-type M-dwarfs.[...]

Ramachandran, Varsha [Verfasser], e Wolf-Rainer [Akademischer Betreuer] Hamann. "Massive star evolution, star formation, and feedback at low metallicity : quantitative spectroscopy of OB stars in the Magellanic Clouds / Varsha Ramachandran ; Betreuer: Wolf-Rainer Hamann". Potsdam : Universität Potsdam, 2019. http://d-nb.info/1218405058/34.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Kunawicz, Nadya. "Any old iron? : astrochemical modelling of star-forming regions at low metallicity". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/any-old-iron--astrochemical-modelling-of-starforming-regions-at-low-metallicity(2a356b1a-429c-40b5-b9c0-2b4cdab12ea8).html.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Two pseudo-time-dependent chemical models have been utilised - one of a dark cloud,and one of a hot core - in order to model these clouds in low metallicity environments, such as other galaxies. The dark cloud model uses gas-phase chemistry, whereas the hot core model includes both gas-phase and surface chemistry. The simulations have been calculated with varying initial elemental abundances of C, O, N, S and the heavy metals Fe, Mg and Na (henceforth, M). These initial abundances are taken from observations of HII regions in the Galaxy, the Large Magellanic Cloud and the Small Magellanic Cloud. The results have been used to identify species which potentially trace the underlying metallicity in dark clouds and hot cores. In the dark cloud models, the most useful tracers are ratios of two species, notably CO/OH and HCO+/CO, which trace the underlying C and M abundances respectively. In the hot core models, the most useful metallicity tracer species are HNC and NH3. The HNC abundance traces an underlying change in metallicity, independent of any changes to the dust/gas ratio. The NH3 abundance traces the underlying N abundance. The hot core model output abundances were used with RATRAN, a non-LTE radiative transfer code, to predict the integrated intensity as a function of hot core radius for various species. The RATRAN results are more directly comparable with observations than the results from the chemical models. Less common isotopes have been used to limit the optical depth of the species modelled. The results show that the extent of the emission may not reflect the size of the hot core. HN13C and NH3 are confirmed as the most useful metallicity tracer species in hot cores.

Lombardo, Linda. "Explorer l'histoire de la Galaxie grâce à la spectroscopie stellaire". Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. http://www.theses.fr/2022UPSLO011.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Ce travail de thèse présente plusieurs études qui utilisent la spectroscopie à haute résolution pour déterminer les propriétés chimiques des différentes populations stellaires de la Voie Lactée. Le document est structuré comme suit : Le premier chapitre de la thèse, divisée en 3 sections, est une introduction générale à la structure de la Voie lactée et à ses populations stellaires, suivie d'une partie décrivant les différentes méthodes utilisées pour mesurer les abondances chimiques des étoiles. La première section décrit les différents scénarios concernant la structure et la formation de la Voie Lactée, en présentant en particulier les découvertes les plus récentes. La deuxième section introduit les concepts physiques de base nécessaires et les objectifs des études présentes dans ce travail de thèse. La troisième section décrit les méthodes utilisées dans l'analyse des données spectroscopiques.Le deuxième chapitre présente les travaux effectués dans la cadre du projet MINCE. La première étude concerne l'analyse de la composition chimique d'un échantillon d'étoiles géantes jeunes qui ont été découvertes par hasard au cours des premières missions d'observations du projet MINCE. J'ai déterminé les paramètres stellaires, analysé les spectres, mesuré les vitesses de rotation de ces étoiles et comparé les résultats aux modèles théoriques, en reportant tous ces résultats dans un article. La deuxième étude présente les résultats obtenus par l'analyse du premier échantillon d'étoiles propres au projet MINCE. J'ai contribué à l'analyse d'une partie des spectres stellaires de ce tout premier jeu de spectres MINCE.Le troisième chapitre porte sur les résultats d'une analyse faite dans le contexte du projet CERES. La première partie de ce travail présente une détermination détaillée de la composition chimique de l'étoile RAVE J110842.1-715300, dont le but est de savoir si cette étoile provient de l'amas globulaire Omega Centauri. Ma contribution porte sur la détermination des paramètres stellaires de cette étoile. La deuxième étude menée dans le contexte de ce projet CERES est constituée de l'analyse d'un échantillon d'étoiles. J'ai déterminé les paramètres stellaires, calculé les modèles d'atmosphère et les abondances chimiques, et écrit l'article. Le quatrième chapitre porte sur un travail fait dans le contexte du projet "High-speed stars" s'intéressant aux étoiles à grande vitesse transversales héliocentriques (>= 500 km/s). La première étude porte sur le suivi spectroscopique à haute résolution de deux étoiles jeunes et pauvres en métaux de l'échantillon de Caffau et al. (2020), afin de déterminer si ces étoiles sont des "blue stragglers". J'ai obtenu et analysé les spectres UVES de ces deux étoiles. Les résultats ne sont pas encore publiés. La deuxième étude concerne une analyse détaillée de deux étoiles à grande vitesse observées avec le spectrographe HDS au télescope Subaru. Pour cette étude, j'ai déterminé l'abondance du Carbone.Le cinquième chapitre présente les résultats obtenus à partir de l'analyse d'un échantillon d'étoiles sélectionnées au moyen de la photométrie de PRISTINE. La première étude porte sur la détermination de la composition chimique d'un échantillon d'étoiles qui ont pu être enrichies par les éjectae de l'explosion de supernovae à instabilité de paires. Mon travail a consisté à sélectionner les candidats les plus intéressants, puis d'effectuer une mission d' observation avec le spectrographe SOPHIE à l'Observatoire de le Haute Provence (OHP). La deuxième étude présente les résultats préliminaires de la détermination de la composition chimique d'un échantillon d'étoiles Pristine sélectionnées comme extrêmement pauvres en métaux. Mon travail a porté sur la détermination des paramètres stellaires et le calcul des abondances chimiques. Un article est en préparation.Le sixième chapitre présente les conclusions de ce travail de thèse et apporte quelques reflexions sur les projets à venir
This thesis project presents several studies that are focused on the investigation of the chemical properties of different stellar populations in the Milky Way by means of high-resolution spectroscopy.The thesis is structured as follows:The first chapter is an introduction to the thesis project, and is divided into three sections. The first section describes the structure and formation scenarios of the Milky Way, in particular by referring to the most recent discoveries. The second section introduces the basic concepts and objectives of the studies presented in this thesis work. The third section describes the methods used to analyse the spectroscopic data.The second chapter presents the studies carried out in the context of the MINCE project. The first study is devoted to the chemical analysis of a sample of young giant stars that was serendipitously discovered during the first MINCE observations. My contribution in this work was to derive the stellar parameters, analyse the spectroscopic data, measure the rotational velocities, compare the results with theoretical models and write the paper. The second study presents the results obtained from the analysis of the first sample of MINCE stars. In this work, I contributed to the analysis of some of the stars in the sample.The third chapter presents the results obtained in the context of the CERES project. The first study presents a detailed chemical analysis of the star RAVE J110842.1-715300, with the aim of understanding whether or not it originated in the Omega Centauri globular cluster. My contribution in this study was to derive the stellar parameters of the star. The second study presents the results obtained for the CERES star sample. My contribution was to derive the parameters, compute model atmospheres, measure the chemical abundances, and write the paper.The fourth chapter presents the results obtained in the context of the High-speed stars project. The first study reports the results obtained from the high-resolution follow-up of two young and metal-poor stars in the sample of Caffau et al. (2020), to check whether they are blue stragglers or not. My contribution in this study was to obtain the high-resolution observations with UVES and to analyse the data. These results have not been published yet. The second study presents a detailed analysis of two high-speed stars observed with Subaru. In this study I was involved in the C abundance determination.The fifth chapter presents the results obtained from the chemical analysis of samples of stars selected using the Pristine photometry. The first study presents the chemical analysis of a sample of metal-poor stars that may have been enriched by the explosion of pair instability supernovae. My contribution was to select promising candidates and observe them with the SOPHIE spectrographat Observatoire de le Haute Provence (OHP)in visitor mode. The second study presents the preliminary results obtained from the chemical analysis of a sample of Pristine extremely metal-poor candidates. My contribution in this study was to derive the stellar parameters and the chemical abundances. The paper is in preparation.The sixth chapter concludes the thesis and gathers final reflections and future projects

Più fonti

Libri sul tema "Stars of low metallicity":

United States. National Aeronautics and Space Administration., a cura di. Chromospherically active stars. Washington, DC: National Aeronautics and Space Administration, 1993.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

United States. National Aeronautics and Space Administration., a cura di. Chromospherically active stars. Washington, DC: National Aeronautics and Space Administration, 1993.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

NATO Advanced Study Institute on Formation and Evolution of Low Mass Stars (1987 Viana do Castelo, Portugal). Formation and evolution of low mass stars. Dordrecht: Kluwer Academic Publishers, 1988.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

R, Rebolo, Zapatero Osorio Maria Rosa e "Three-Islands" Euroconference on "Stellar Clusters and Associations" (1st : 1998 : Palma, Canary Islands), a cura di. Very low-mass stars and brown dwarfs. Cambridge: Cambridge University Press, 2000.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Dupree, A. K., e M. T. V. T. Lago, a cura di. Formation and Evolution of Low Mass Stars. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-3037-7.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Reid, I. Neill. New light on dark stars: Red dwarfs, low-mass stars, brown dwarfs. New York: Springer, 2000.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Hill, Randal C. Spotlight on sports stars. [Austin, Tex.]: Steck-Vaughn Co., 1989.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Prusti, Timo Juhani. Infrared studies of low mass formation. [Groningen, Netherlands]: Rijksuniversiteit Groningen, 1992.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Reipurth, Bo, e Claude Bertout, a cura di. Herbig-Haro Flows and the Birth of Low Mass Stars. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5608-0.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

W, Romani Roger, e United States. National Aeronautics and Space Administration., a cura di. EUV/soft x-ray spectra for low B neutron stars. [Washington, DC: National Aeronautics and Space Administration, 1995.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Più fonti

Capitoli di libri sul tema "Stars of low metallicity":

Beers, T. C. "The Metallicity Distribution Function of Extremely Low-Metallicity Stars". In Galaxy Evolution: Connecting the Distant Universe with the Local Fossil Record, 105–13. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4213-7_18.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Duncan, D. "Key Questions for Low Metallicity Stars". In Space Sciences Series of ISSI, 167–74. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5116-0_17.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Ann, Hong Bae, e Yong Hee Kang. "Age-Metallicity Relation for F-Stars". In Third Asian-Pacific Regional Meeting of the International Astronomical Union, 325–27. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4496-1_50.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Beers, T. C., S. Rossi, J. E. Norris, S. G. Ryan, P. Molaro e R. Rebolo. "The Low Metallicity Tail of the Halo Metallicity Distribution Function". In Space Sciences Series of ISSI, 139–44. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5116-0_13.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Castro, S., B. Barbuy e T. Richtler. "Metallicity of Two Stars in Baade’s Window". In Galactic Bulges, 295–96. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-0922-2_25.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Peterson, R. C. "Disentangling Metallicity and Age for Turnoff Stars". In Galaxy Evolution: Connecting the Distant Universe with the Local Fossil Record, 427–30. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4213-7_89.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Prantzos, Nikos. "Stars (Low Mass)". In Encyclopedia of Astrobiology, 1575. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_1505.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Jahreiss, Hartmut. "Low Mass Stars". In Science with Astronomical Near-Infrared Sky Surveys, 63–68. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-0946-8_14.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Nissen, P. E. "Age and Metallicity Distributions Among Galactic Disk Stars". In Stellar Populations, 109–17. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0125-7_10.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Hernández, X., e A. Ferrara. "Cosmological Origin of the Lowest Metallicity Halo Stars". In New Quests in Stellar Astrophysics: The Link Between Stars and Cosmology, 69–72. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0393-3_13.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Atti di convegni sul tema "Stars of low metallicity":

de Mink, S. E., M. Cottaar e O. R. Pols. "Can Low—Metallicity Binaries Avoid Merging?" In FIRST STARS III: First Stars II Conference. American Institute of Physics, 2008. http://dx.doi.org/10.1063/1.2905545.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Pignatari, M., e R. Gallino. "The Weak s‐Process at Low Metallicity". In FIRST STARS III: First Stars II Conference. American Institute of Physics, 2008. http://dx.doi.org/10.1063/1.2905575.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Lai, David K., Sara Lucatello, Michael Bolte, Debra A. Fischer e Jennifer A. Johnson. "A Search for Binary Stars at Low Metallicity". In FIRST STARS III: First Stars II Conference. American Institute of Physics, 2008. http://dx.doi.org/10.1063/1.2905523.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Omukai, Kazu, Naoki Yoshida, Daniel J. Whalen, Volker Bromm e Naoki Yoshida. "Low-Metallicity Star Formation". In THE FIRST STARS AND GALAXIES: CHALLENGES FOR THE NEXT DECADE. AIP, 2010. http://dx.doi.org/10.1063/1.3518838.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Stancliffe, Richard J., Maria A. Lugaro, Amanda I. Karakas e Carlos Rijs. "The s-process at low metallicity". In FIRST STARS IV – FROM HAYASHI TO THE FUTURE –. AIP, 2012. http://dx.doi.org/10.1063/1.4754347.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Iwamoto, Nobuyuki, Takuma Suda, Takaya Nozawa, Akira Ohnishi, Kiyoshi Kato, Masayuki Y. Fujimoto, Toshitaka Kajino e Shigeru Kubono. "Lithium synthesis in low metallicity AGB stars". In ORIGIN OF MATTER AND EVOLUTION OF GALAXIES: The 10th International Symposium on Origin of Matter and Evolution of Galaxies: From the Dawn of Universe to the Formation of Solar System. AIP, 2008. http://dx.doi.org/10.1063/1.2943562.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Hirschi, Raphael, Cristina Chiappini, Georges Meynet, Sylvia Ekström, André Maeder, Richard J. Stancliffe, Guenter Houdek, Rebecca G. Martin e Christopher A. Tout. "Mass Loss and Very Low-metallicity Stars". In UNSOLVED PROBLEMS IN STELLAR PHYSICS: A Conference in Honor of Douglas Gough. AIP, 2007. http://dx.doi.org/10.1063/1.2818999.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Yoon, S. ‐C, M. Cantiello e N. Langer. "Evolution of Massive Stars at Very Low Metallicity, Including Rotation and Binary Interactions". In FIRST STARS III: First Stars II Conference. American Institute of Physics, 2008. http://dx.doi.org/10.1063/1.2905548.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

de Mink, S. E., O. R. Pols e S. ‐C Yoon. "Binaries at Low Metallicity: Ranges For Case A, B and C Mass Transfer". In FIRST STARS III: First Stars II Conference. American Institute of Physics, 2008. http://dx.doi.org/10.1063/1.2905549.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Doi, Kentaro, Hajime Susa e Kazuyuki Omukai. "Dissipation of magnetic fields in low-metallicity clouds". In FIRST STARS IV – FROM HAYASHI TO THE FUTURE –. AIP, 2012. http://dx.doi.org/10.1063/1.4754383.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Rapporti di organizzazioni sul tema "Stars of low metallicity":

Whitaker, Stephen. Rocky intertidal community monitoring at Channel Islands National Park: 2018–19 annual report. National Park Service, agosto 2023. http://dx.doi.org/10.36967/2299674.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Abstract (sommario):

Channel Islands National Park includes the five northern islands off the coast of southern California (San Miguel, Santa Rosa, Santa Cruz, Anacapa, and Santa Barbara Islands) and the surrounding waters out one nautical mile. There are approximately 176 miles of coastline around the islands, about 80% of which is composed of rock. The diversity and undisturbed nature of the tidepools of this rocky coastline were recognized as special features of the islands in the enabling legislation. To conserve these communities unimpaired for future generations, the National Park Service has been monitoring the rocky intertidal communities at the islands since 1982. Sites were established between 1982 and 1998. Site selection considered visitation, accessibility, presence of representative organisms, wildlife disturbance, and safety. This report summarizes the 2018–2019 sampling year efforts (from November 2018 to April 2019) and findings of the Channel Islands National Park Rocky Intertidal Community Monitoring Program. Specific monitoring objectives are 1) to determine the long-term trends in percent cover of key sessile organisms in the rocky intertidal ecosystem, and 2) to determine population dynamics of black abalone (Haliotis cracherodii), owl limpets (Lottia gigantea), and ochre sea stars (Pisaster ochraceus). Objectives were met by monitoring percent cover of core species in target intertidal zones using photoplots and transects, and by measuring size frequency and abundance of black abalone, owl limpets, and sea stars using fixed plots or timed searches. Twelve key species or assemblages, as well as the substrate, tar, have been monitored twice per year at 21 sites on the five park islands as part of the rocky intertidal community monitoring program. Fixed photoplots were used to monitor the percent cover of thatched and acorn barnacles (Tetraclita rubescens, Balanus glandula/Chthamalus spp., respectively), mussels (Mytilus californianus), rockweeds (Silvetia compressa, and Pelvetiopsis californica (formerly Hesperophycus californicus), turfweed (Endocladia muricata), goose barnacles (Pollicipes polymerus) and tar. Point-intercept transects were used to determine the percent cover of surfgrass (Phyllospadix spp.). Information about size distribution (i.e., “size frequency” data) was collected for owl limpets in circular plots. Size distribution and relative abundance of black abalone and ochre sea stars were determined using timed searches. The maximum number of shorebirds and pinnipeds seen at one time were counted at each site. The number of concession boat visitors to the Anacapa tidepools was collected and reported. All sites were monitored in 2018–2019. This was the third year that we officially reduced our sampling interval from twice per year (spring and fall) to once in order to streamline the program and allow for the implementation of additional protocols. Weather conditions during the site visits were satisfactory, but high wind coupled with strong swell and surge limited or prevented the completion of some of the abalone and sea star searches. The percent cover for most key species or assemblages targeted in the photoplots was highly variable among sites. Mussel (Mytilus californianus) cover remained below average at Anacapa and Santa Barbara Islands. Record or near record low abundances for Mytilus were measured at Middle West Anacapa (Anacapa Island), Harris Point (San Miguel Island), Prisoner’s Harbor (Santa Cruz Island), and Sea Lion Rookery (Santa Barbara Island) sites. The only site that appeared to have above average Mytilus cover was Scorpion Rock on Santa Cruz Island. All other sites had mussel cover near or below the long-term mean. Qualitatively, Mytilus recruitment appeared low at most sites. Both rockweed species, Silvetia compressa and Pelvetiopsis californica (formerly Hesperophycus californicus), continued to decrease markedly in abundance this year at the majority of sites compared to combined averages for previous years. Fossil Reef and Northwest-Talcott on Santa Rosa Island, Sea Lion Rookery on Santa Barbara Island, and South Frenchy’s Cove on Anacapa Island were the only sites that supported Silvetia cover that was near the long-term mean. No sites exhibited above average cover of rockweed. Extremely high levels of recruitment for Silvetia and Pelvetiopsis were documented at many sites. Most sites exhibited marked declines in S. compressa abundances beginning in the early 2000s, with little recovery observed for the rockweed through this year. Barnacle (Chthamalus/Balanus spp.) cover fell below the long-term means at all islands except Anacapa, where barnacle cover was slightly above average. Endocladia muricata abundances remained comparable to the grand mean calculated for previous years at Santa Barbara, Santa Cruz, and Santa Rosa Islands, while cover of the alga decreased slightly below the long-term means at Anacapa and San Miguel Islands. Black abalone (Haliotis cracherodii) abundances at the islands remain less than one percent of 1985 population levels. Zero abalone were found throughout the entire site at Landing Cove on Santa Barbara Island and South Frenchy’s Cove on Anacapa Island. Above average abundances relative to the long-term mean generated from post-1995 data were observed at all but five sites. Juvenile black abalone were seen at all islands except Santa Barbara. Ochre sea star (Pisaster ochraceus) populations crashed in 2014 at all monitoring sites due to Sea Star Wasting Syndrome, an illness characterized by a suite of symptoms that generally result in death. The mortality event was widely considered to be the largest mortality event for marine diseases ever seen. Beginning in June 2013, the disease swiftly and significantly impacted P. ochraceus (among other species of sea stars) populations along the North American Pacific coast from Alaska to Baja California, Mexico. By the beginning of 2014, P. ochraceus abundances had declined by >95% at nearly all Channel Islands long-term intertidal monitoring sites, in addition to numerous other locations along the West Coast. At various times during the past decade, extremely high abundances (~ 500 P. ochraceus) have been observed at multiple sites, and most locations have supported >100 sea stars counted during 30-minute site-wide searches. This year, abundances ranged 0–13 individuals per site with all but one site having fewer than 10 P. ochraceus seen during routine searches. Insufficient numbers of sea stars were seen to accurately estimate the size structure of P. ochraceus populations. Only two juveniles (i.e., <50 mm) were observed at all sites combined. Giant owl limpet densities in 2018–2019 were comparable or slightly above the long-term mean at seven sites. Exceptionally high densities were measured at Northwest-Talcott on Santa Rosa Island, Otter Harbor on San Miguel Island, and Willows Anchorage on Santa Cruz Island. The sizes of L. gigantea this year varied among sites and islands. The smallest L. gigantea were observed at Otter Harbor followed closely by Willows Anchorage and Anacapa Middle West, and the largest were seen at Northwest-Talcott. Temporally, the mean sizes of L. gigantea in 2018–2019 decreased below the long-term mean at each island except Anacapa. Surfgrasses (Phyllospadix spp.) are typically monitored biannually at two sites each on Santa Cruz and Santa Rosa Islands. Beginning in 2015, all transects at each of the monitoring sites were only sampled once per year. At East Point on Santa Rosa Island, the conditions were not conducive to sampling the surfgrass transects, but qualitatively, percent cover of surfgrass appeared to be near 100% on all three transects. Relative to past years, cover of surfgrass increased above the long-term mean at Fraser Cove on Santa Cruz Island, fell slightly below the mean at Trailer on Santa Cruz Island, and remained approximately equivalent to the mean at the two Santa Rosa Island sites. Overall, the abundance and diversity of shorebirds in 2018–2019 at all sites appeared similar to observations made in recent years, with the exception of elevated numbers of brown pelicans (Pelecanus occidentalis) observed at East Point on Santa Rosa Island. Black oystercatchers (Haematopus bachmani) were the most ubiquitous shorebird seen at all sites. Black turnstones (Arenaria melanocephala) were not common relative to past years. Pinniped abundances remained comparable in 2018–2019 to historical counts for all three species that are commonly seen at the islands. Harbor seals (Phoca vitulina) were seen in the vicinity of eight sites this year. As in past years, harbor seals were most abundant at Otter Harbor and Harris Point on San Miguel Island. Elephant seals (Mirounga angustirostris) were seen at six sites during the year, where abundances ranged 1–5 individuals per location. California sea lions (Zalophus californianus) were common at Santa Barbara Island; 117 individuals were observed at Sea Lion Rookery. Sea lion abundances were higher than usual at Harris Point (N = 160) and Otter Harbor (N = 82) on San Miguel Island. Relative to past years, abundances this year were considered average at other locations.